1. Field of the Invention
This invention relates to the field of electromagnetic fluid treatment devices for decreasing accumulation of hard scale, lime and similar deposits via electromagnetic agitation of mineral ions in fluid supply conduits. The invention relates more particularly to a clamp-on magnetic device using a specific magnet array and housing.
2. Prior Art
Numerous attempts have been made to treat water and other fluids by means of electric and magnetic interactions with the fluid. Dissolved mineral deposits in a water supply appear as free ions (charged particles), which can be moved electromagnetically. Electrostatic forces can separate ions by their charge. Flow of ions along the fluid flow path defines a current, making it also possible to affect the mobility of ions in the fluid magnetically. The Hall effect, for example, will cause a transverse force to act on moving charges subjected to a magnetic field. This force can be applied using a non-varying magnetic field, for example from permanent magnets, to agitate ions moving along the flow path.
Agitating ions, per se, does not make the ions unavailable for the chemical reactions which result in precipitation of lime and scale. However, in practice, it has been determined by various persons in the art that the character of the precipitation of lime and scale deposits, such as calcium carbonate in domestic water supplies, can be altered with beneficial results, using electric and magnetic fields. In particular, when magnetic fields are applied to a flow of ion-containing fluid, agitation of the ions causes the inevitable precipitate to be more sludge-like, loosely associated and less capable of forming the type of hard scale precipitate accumulations which adversely affect the flow path. Adverse effects of hard scale are due to their clinging nature, not due to their existence, per se. Problems include reduction of the internal diameter of the conduit, decrease in thermal conductivity of the conduit, and the like. These problems do not occur where the precipitate does not become fixed in a scaly accumulation and instead is flushed along with the flow.
The foregoing beneficial effects of magnetic treatment are known in the prior art. However, the particular means for producing the required fields and the field strengths have typically been both overly complicated and incapable of producing the required high magnetic flux density needed to render the device operable and practical. One group of devices for water treatment is characterized by complex housings and flow path-defining elements which must be inserted in-line along the flow path, i.e., by removing a section of conduit, and installing a plumbed-in fixture. While it may be possible with such a device to achieve adequate flux density, as a practical matter, the device is too complicated.
Moody U.S. Pat. No. 3,228,878 discloses a water treatment device wherein a plurality of permanent magnets are clamped on a conduit to define a zone subjected to a stable magnetic field. In this patent, the magnets are bar magnets in an arched configuration, a plurality of such magnets being attached such that all the magnets have their south poles at the same place along the flowpath, i.e., around one circumferential position along the conduit, and all the north poles are likewise together, at a circumferential position downstream of the south poles. Such a device would seem to be a straightforward solution to the problem of applying a magnetic field to a conduit. However, by placing all the like poles of the magnets together, a null is produced, particularly centrally in the conduit, wherein the flux density is at a minimum.
Another drawback to the prior art structure of Moody, and other devices characterized by a group of similar poles placed together, occurs because the flux density of a magnetic field is most concentrated through material of maximum magnetic permeability between the opposite magnetic poles, while the lines of flux diverge in low-permeability areas, e.g., air gaps between the poles. The energy associated with the magnetic field in Moody tends to reside in the relatively long gap between the successively-placed opposite poles, where the lines of flux diverge, rather than across the shorter gap defined transversely across the fluid conduit. Therefore, the type of device as disclosed in Moody '878 is insufficient because an unnecessarily long gap is left between opposite magnetic poles.
Green et al U.S. Pat. No. 2,939,830 teaches a device wherein a magnetic pole piece extends internally. Electric means are provided for energizing the pole piece using an alternating current. While it is possible to minimize the low permeability gap in a water treatment device by providing internal high permeability structures for confining magnetic flux lines, this is an unacceptable solution because devices of this type must inherently be attached in-line in the conduit, i.e., the fixture must be plumbed-in.
In another class of devices, a plurality of semicircular annular magnets are placed on a conduit means. In Granger U.S. Pat. No. 4,229,389, an in-line device employs such magnets, in an alternating-pole arrangement.
Carpenter Pat. No. 4,367,143 discloses a clamp-on device having a plurality of permanent magnets with means for clamping the magnets to the outside of a section of conduit. This device, like the Moody device, places like poles across from one another in the direction transverse to the flow path. Moreover, the Carpenter device employs three magnets at 120 degree interval
Fujita Pat. No. 4,188,296 discloses a magnet treatment device wherein the lines of flux pass transversely through a conduit. However, there is no reversal of polarity proceeding along the flow path. Hall effect forces on ions in fluid passing along the conduit will not be reversed. The effect of the device is therefore simply to induce eddies at one point along the flow path.
Each of the foregoing patent disclosures is incorporated for teachings related to magnetic water treatment. The present invention, however, is directed to improving such devices by increasing the agitation of calcareous water ions in a device which is minimally intrusive of the fluid conduit system. This is accomplished using an array of magnets which is self-clamping, i.e., having opposite magnetic poles facing one another transversely across the flow path defined by the conduit. Individual permanent magnets in the array are polarized in a direction oriented toward and away from the conduit, and not along a direction parallel to the longitudinal axis of the conduit. Downstream from a first array of at least two magnets having opposite poles facing across the conduit, is a second array having a similar configuration, but reversed in direction from the first array.
The invention also includes a housing element of ferrous material which bridges the poles of the magnetic array which face diametrically away from the conduit. Because the housing is a high permeability material, substantially all the magnetic energy is concentrated in a transverse magnetic field perpendicular to the fluid flow path through the conduit. It is therefore possible with relatively inexpensive permanent magnets to achieve a high flux density and to produce sufficient agitation to have a beneficial effect, even at the relatively low velocity of fluid moving in the flow path of a typical domestic water supply.